title: Utility of cystatin C for renal function in amyotrophic lateral sclerosis.
abstract: OBJECTIVE
  Creatinine (Cr) as a marker of renal function has limited value in amyotrophic lateral sclerosis (ALS) because patients with ALS have reduced muscle mass. Thus, there is a need for alternative methods of assessing renal function. Cystatin C (CysC), which is unaffected by muscle mass, is potentially an ideal biomarker of nephrotoxicity in ALS; however, its utility requires validation.
  
  
  METHODS
  One hundred and six subjects were recruited for the study: 76 ALS patients and 30 healthy controls. We compared the Cr-based estimated glomerular filtration rate (eGFR) with the CysC-based eGFR in the ALS patients and healthy controls. The results were further analysed according to the severity of ALS in the patients.
  
  
  RESULTS
  The mean Cr-based eGFRs were 257.2 ± 383.1 ml/min/1.73 m(2) in the ALS group and 98.1 ± 34.9 in the control group; however, the mean CysC-based eGFRs were not significantly different between both groups. Thus, the Cr-based eGFR in the ALS group was markedly higher than any of the other values. Although serum CysC levels did not correlate with the severity of ALS according to the ALS Functional Rating Scale-Revised, strong simple correlations were observed between serum Cr levels and the severity of ALS (correlation coefficient = 0.734, P < 0.001).
  
  
  CONCLUSIONS
  This study demonstrates the potential usefulness of CysC as a biomarker of renal function in ALS patients. Furthermore, its applicability could be extended to other neuromuscular diseases.
authors.affiliation: Division of Neurology, Department of Internal Medicine, Jichi Medical University, Shimotsuke, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Tetsuka
authors.forename: M
authors.initials: M
authors.lastname: Morita
authors.forename: K
authors.initials: K
authors.lastname: Ikeguchi
authors.forename: I
authors.initials: I
authors.lastname: Nakano
mesh_terms: D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000097:blood / Q000150:complications*; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000097:blood / Q000175:diagnosis / Q000209:etiology; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index
chemical_list: D055316:Cystatin C; D003404:Creatinine
keywords: amyotrophic lateral sclerosis; creatinine; cystatin C; estimated glomerular filtration rates; renal function